At present, the traditionally used main manufacturing process for producing a color film layer on a color filter is the pigment dispersing process, whose basic principle includes the steps of coating a pigment light-blocking agent onto a transparent substrate, and then irritating the same with a ray such as the ray from an ultraviolet lamp so as to cure the pigment light-blocking agent and form the color film layer. The pigment light-blocking agent comprises a pigment dispersion, a monomer, an oligomer, a diluent, a leveling agent and a solvent or the like, and the pigment dispersion mainly comprises a colored pigment, a dispersant, a resin and a solvent. The stability of the pigment dispersion is very important. If there are precipitates produced in the pigment dispersion, the pigment light-blocking agent prepared by using this pigment dispersion will also produce precipitates, which will cause directly the surface of the color film layer on the color filter uneven, apt to produce mura, and thus, the qualified ratio of the product will be decreased. If there is the phenomenon of agglomeration in the pigment dispersion, such pigment dispersion cannot be used for formulating the pigment light-blocking agent.
Pigment powders are generally consisted of 0.02-0.5 μm fine crystal grains. There is a strong trend of aggregation and agglomeration among the crystal grains due to the small particle diameter, large specific surface area and high interface energy of the crystal grains. In order to qualify the contrast degree of a color filter, the particle diameter of the pigment in a pigment light-blocking agent is generally required to be tens of nanometers. Thus, in the preparation process of a pigment dispersion, the surface of the pigment should be further treated so as to make it stable in a range of tens of nanometers. In order to prevent the agglomeration of pigment particles, for example, the pigment is subjected to an inorganic acid treatment, a mechanical graining process, or a treatment in which an additive such as a dispersant, a resin and a low molecular compound of a pigment derivative or the like is added. Still, there have been not reported a process for effectively improving the stability of a pigment dispersion at present.